This invention relates generally to deformation imaging.
Deformation imaging may be generally described as a technique for recording images on a deformable layer by the combined application of an electrostatic field and a softening influence on the deformable layer. For example, two such techniques are known as "relief" imaging and "frost" imaging. These techniques basically involve applying a latent electrostatic image or a charge pattern to an insulating deformable layer which is softened by the application of heat or solvent vapor, softening the deformable layer until the electric field force of the charge pattern deforms the layer and then rigidifying the layer in its deformed state.
In frost imaging, the deformation comprises a series of very small surface folds or wrinkles with the depth of the folds in any particular surface location dependent upon the amount of charge in that area. The image produced has a frosted appearance, has good continuous tone response and solid area coverage. Relief imaging, on the other hand, produces ridge-like deformations in the deformable layer at the situs of potential gradients in the applied charge pattern, exhibiting an edge effect. Thus, relief imaging is most suitable for the reproduction of high contrast subjects such as line copy or the like. Other deformation imaging techniques, such as that described in U.S. Pat. No. 2,896,507 have been devised and are suitable for use with the instant invention.
Once a deformation image is formed, it may be fixed by allowing or causing the film to reharden by removal of heat or solvent vapors, or by cooling if necessary. It is also possible to erase such images after they have been viewed by simply resoftening the film and maintaining a low viscosity for a sufficient period of time. Discharge is believed to occur by fluid migration of the ions making up the charge pattern from the top surface of the deformed film while it is still soft during initial deformation. Surface tension forces restore a smooth surface to the film on resoftening, so that it is ready for reuse in the system.
The ability to see images of this type is based on the deformed surfaces serving as light scattering centers changing the angles of reflection or transmission of incident light. Of course, the characteristics of the deformation images are dependent upon the optical system employed in projecting the image to be reproduced by deformation onto the surface of the deformable layer. Some such systems utilize optical screens and filters to extend dynamic range, such as U.S. Pat. No. 3,698,,892, filed Apr. 10, 1970. However, these systems do involve the loss of some radiation by reflection or absorption by the screen or filter.
One additional type of deformation imaging member to which the instant invention applies is called a Ruticon. Such a device is disclosed in U.S. Pat. No. 3,716,359 which is hereby expressly incorporated herein by reference. Ruticons are solid-state cyclic image recording devices. They have a layered structure comprised of a conductive transparent substrate, a thin photo-conductive layer, a thin deformable elastomer layer, and a deformable electrode such as a conductive liquid, a conductive gas, or a thin flexible metal layer. When an electric field is placed between the conductive substrate and the deformable electrode the elastomer will deform into a surface relief pattern corresponding to the light intensity distribution of an image focused on the photoconductor. Light modulated by the deformation of the elastomer surface can, in turn, be converted to an intensity distribution similar to the original image by means of simple optics. Ruticons have numerous useful applications such as image intensification, holographic recording and optical buffer storage systems.
The general basis of the instant invention lies in the use of lenses to redirect radiation into a predetermined configuration. Theoretically, a perfect lens is one which shows an image of a point as a point, and a straight line as a straight line. But in practice, the lenses are never perfect; they reproduce a point as a patch, and a straight line as a more less curved band. The problems associated with lenses are inherent in the construction, and an optical system designer controls most of the aberrations by combining a number of single lenses such that the aberrations of one lens tend to cancel out the aberrations of another lens.
Axial aberrations are aberrations which affect an image point on the axis of the lens. The two principal axial aberrations are chromatic aberrations and spherical aberrations. Chromatic aberrations merely reflect the fact that a single lens made from a single type of optical glass will refract blue rays more strongly than green rays, which in turn are refracted more strongly than red rays. Thus, a three dimensional spacial positioning of the colored rays results from and is referred to as, chromatic aberration. Spherical aberration involves the phenomenon that rays coming from an object on the axis of a lens and going through the center of the lens come to a focus at a certain point on the axis of the lens. Rays from an axial object going through the lens near the edges should come to a focus at the same point, but in practice, because of spherical aberration, they tend to come toward a different point of focus. The difference between these focal points is the spherical aberration of the lens. Spherical aberration increases with the lens aperture. In a simple converging lens, spherical aberration causes the rays farthest from the lens axis to converge more strongly, and come to a focus nearer the lens than the central rays close to the lens axis. The image is never fully sharp. Spherical aberration does not vary with image size, but rather varies to the square of the aperture.
More specifically, the instant invention is concerned with the use of lenticular lens systems as a means of redirecting imaged light rays. A lenticular system is one which employs a lenticular screen to break up an image into linear and area components which are subsequently combined. The purpose of splitting is usually to accommodate two or more images interspersed in each other on the same area. Uses of a lenticular screen or lenticular system are usually for lenticular color photography, stereo photography, image disection, and multiple image storage.
The main component of a lenticular system is the lenticular element itself, consisting of a transparent support embossed with a regular screen of lens surfaces. Usually these are cylindrical running across the screen in one direction of strips. By embossing a second set of linear elements that run angularly to the first, another type of lenticular lens, consisting of individual lens elements, is obtained. If the relative angle between the lens arrays is 90.degree., a spherical lenticular lens is created.
When the lenticular element is placed in front of the surface on which the camera lens projects an image, the individual lenticular elements break up the image into lines or points. They concentrate the elements into a smaller area, leaving spaces between them. Additionally, images can be recorded in the spaces by slightly displacing the lens laterally or by moving the object in front of the lens. The record or recorded image then contains a series of interlaced images which can be reconstituted by observation through a similar lenticular screen. The lenticular screen breaks up the image into line elements with spaces between them. If the screen is moved, a new set of line elements is formed in the spaces between the first set.
Lenticular lenses per se are not new in the imaging arts, and have been used for a good number of years to concentrate and intensify light. For example, U.S. Pat. No. 1,824,353, discloses the use of various shaped lenses to accomplish this exact end result. It is to be noted, however, that this patent is limited to the exposure of photographic plates and permits direct viewing of the formed image only through the image forming optical system.
Another patent which broadly teaches the use of lenticular lenses as a means of intensifying light is U.S. Pat. No. 1,849,036. Here again, it should be noted that the disclosure is limited to the exposure of photographic plates and permits direct viewing of the formed image only through the image forming optical system.
Both of the patents discussed immediately above are, like all photographic systems, dependent upon the light absorption characteristics of the film used. This is to be contrasted with the light reflective or scattering characteristics of the deformation imaging films of the instant invention. U.S. Pat. No. 3,413,117 discloses, in FIG. 7, a deformation imaging system employing an integrated lenticular element and single recording layer. The primary concern of this patent is the creation of color images through the use of filters and lenticular screens. It should be noted that read-out is accomplished by illumination through the entire recording number and lenticular element.